Atomistically informed continuum model of polymer-based nanocomposites

A model polymeric material filled with spherical nanoparticles is considered in this work. Monte Carlo simulations are performed to determine the polymer chain conformations in the vicinity of the curved interface with the filler. Several discrete models of increasing complexity are considered: the athermal system with excluded volume interactions only, the system in which entropic and energetic interactions take place while the filler is a purely repulsive sphere, and the system in which both filler-polymer and polymer-polymer energetic interactions are accounted for. The total density, chain end density, chain segment preferential orientation and chain size and shape variation with the distance from the filler wall are determined. The structure is graded, with the thickness of the transition region being dependent on the property and scale considered. Hence, the polymer in the vicinity of the filler is represented in the continuum sense by a material with graded properties whose elasticity is determined based on the local structure. Homogenization theory is the used to obtain the overall composite moduli. The filler size effect on the composite elasticity is evaluated.